During the course of in vitro fertilisation (IVF), gamets and embryos are being handled frequently. The handling implies physical handling, for example moving the cells from one culture dish to another, denudation and Intracytoplasmic Sperm Injection (ICSI) and changes in medium composition and physical parameters such as temperature, pH and osmolarity. Normally, gamets and embryos are kept in 4-well culture dishes or 60 mm Petri dishes or the likes. These systems are regarded as open culture systems and as such, CO2 is very difficult to control, because as soon as the lid is removed from the culture dish, CO2 evaporates leading to a change in pH.
Another very important parameter when culturing is temperature. The temperature is very difficult to control within the medium and during handling of embryos (e.g. changing media, microscopy, denudation). It is not unusually to see temperature fluctuations of more than ±2° C., which can reduce the viability of the cells. Using standard Petri dishes in procedures such as in vitro maturation of eggs, in vitro fertilization, 3-day culturing of embryos, culturing to the blastocysts stage, etc. require handling of the individual cells/embryos several times for each procedure. How much this reduces the potential of the cells is difficult to say, but each time the embryo is being handled, it involves a risk of physical damage, a change in temperature and pH and contamination from the surroundings, which all are factors reducing the viability of the cell or the implantation potential of the embryo. Thus, there is a need for designing a culture dish that can optimize culture conditions during IVF.
Additionally, practical handling of the conventional dishes is not optimum. In order to lift a dish, one must lift both the bottom of the dish and the lid at the same time. If the operator is not careful, the operator will only lift the lid with the result that the dish is dropped.
Despite the increase of the industry related to IVF, advantage is primarily taken of general experience in in-vitro cell culturing and only relatively few attempts have been made to develop apparatus especially designed and optimised for IVF.
US patent application no. 2002/0187078 A1 describes a multi-well plate for holding a chemical compound for heating in a microwave oven. The plate is a planer member having arrays of rows and columns in its surface. The plate has heat reservoirs in the form of fluid filled channels positioned lengthwise along the side portions of the plate.
U.S. Pat. No. 4,786,601 describes a tissue culture holder which has an insulating chamber in its base below the culture wells. The insulating chamber is filled with air or a clear liquid, and it may be sealed or may have passageways for circulating air through the chamber and up into the space above the wells.
U.S. Pat. No. 5,876,675 describes a microfluidic device. One embodiment of the invention relates to a microfluidic device, which incorporates a manual handling structure. This manual handling structure is shown as inwardly tapered or insert edges, at opposing edges of the device.
Especially designed for IVF are aspects in the following disclosures with compartments to culture embryonic cells.
U.S. Pat. No. 5,484,731 describes a multi-well In Vitro Fertilization (IVF) plate. The plate is equipped with a removable lid divided into adequate sections. Each section may be moved by a sliding movement from a closed position into an open position, thereby each exposing a plurality of wells.
U.S. Pat. No. 6,448,069 describes an embryo culturing method and apparatus including a culturing container such as a Petri dish. The culturing container contains a number of compartments made from a plurality of spaced-apart pickets which combine to form four compartments. The pickets serve to form liquid permeable barriers between adjacent compartments, and also between the growth enhancing nutrient.
U.S. Pat. No. 5,449,620 describes a method and apparatus for culturing embryonic system cells. The apparatus provided in this invention comprises a solid support such as a Petri dish having a plurality of tapered depressions in the bottom wherein a controlled concentration of a selected cell-type may be layered into each depression. The depressions have a diameter of about 0.2-0.3 mm at the top and 0.1-0.2 mm at the bottom.
U.S. Pat. No. 5,627,066 describes a method and apparatus for In Vitro Fertilization. The apparatus provided in this invention comprises a culture dish which is equipped with a number of micro-chambers. Each micro-chamber has a volume which exceeds the volume of an oocyte to be fertilized. The volume of the chamber is generally 8 to 20 times the volume of an oocyte.
International patent application WO 01/88087 describes an apparatus for micro-fluidic handling of embryonic cells including a transport network formed by a generally embryo scaled channel (micro-channels) is disclosed.
Finnish patent application FI 884 551 by Jukka Häyrinen discloses a culture dish comprising a basic structure with a number of macro wells for culturing oocytes and a rotatable lid with openings adapted to a row of macro wells such that when the opening is aligned with this row of macro wells, access is possible to four macro wells through the opening in the lid. The access to at least four wells at a time leads to unnecessary evaporation of carbon dioxide unnecessary heat loss, which is a disadvantage.
U.S. Pat. No. 5,891,712 discloses a drop culture dish with indentations in the bottom with alphabetical markings.
Micro channels for oocytes are disclosed in S. M. Willadsen “A method for culture of micromanipulated sheep embryos and its use to produce monozygotic twins”. Nature Vol. 277, pp. 298-299, Jan. 25, 1979 and in H. H. van der Ven et al. “Fertilization of human oocytes in capillary tubes with very small numbers of spermatozoa”, Human Reproduction Vol. 4 no. 1 pp. 72-76, 1989. Micro-channels with barriers to hold an oocyte in, while it is exposed to fluid flow through the channel is disclosed in U.S. Pat. No. 6,193,647 or reported in Glasgow et al. “Individual embryo transport and retention on a chip” published in Micro Total Analysis systems 1998, p. 13-18, October 1989, and in H. C. Zeringe et al. “Micro fluidic single embryo in PDMS”, presented at 21st Ann. Int'l. Conf. of the IEEE Eng. in Med. and Bio. Soc. and the 1999 Ann. Fall Meeting of the Biomed. Eng. Society, Atlanta, Ga., Oct. 13-16, 1999.
Though, the abovementioned specially designed culturing dishes have improved the handling of oocytes for IVF, still needs for improvements exist. Especially aspects like reduced evaporation of carbon dioxide, pH stability and reduced heat loss are of concern.